How to post a file via HTTP as multipart/form-data to Facebook?

I would like to post a new photo to a user using `Net::HTTP::multipart`
from a Heroku application to Facebook.

I have the following JSON object:

    {"message"=>"My message",
"image"=>#<ActionDispatch::Http::UploadedFile:0x00000004242490
@original_filename="neEZYMAnBI.jpg",
@content_type="application/octet-stream", @headers="Content-Disposition:
form-data; name=\"image\";
filename=\"/home/user/public/direct/fb_images/neEZYMAnBI.jpg\"\r\nContent-Type:
application/octet-stream\r\n",
@tempfile=#<File:/app/tmp/RackMultipart20110818-1-18qnwtj>>,
"method"=>"post", "access_token"=>"my_access_token", "format"=>"json"}

I tried to use:

    require 'net/http/post/multipart'

    url =
URI.parse('https://graph.facebook.com/me/photos?access_token=#{params[:access_token]}')
    File.open(params[@tempfile]) do |jpg|
      req = Net::HTTP::Post::Multipart.new url.path,
        "file" => UploadIO.new(jpg, "image/jpeg", "image.jpg")
      res = Net::HTTP.start(url.host, url.port) do |http|
        http.request(req)
      end
    end

But:

1. It is not sending the data.
2. I cannot find how to send the params[:message] with the file in
order to have a caption for the image.

Can someone suggest a solution?

Thanks

I think that this can help :

class FbPhotoUploader
  require 'net/http/post/multipart' # multipart-post gem
  require 'mime/types' #mime-types gem
  require 'net/https'

  def upload(path, access_token, options={})
    photo = File.open(path)
    params = {:access_token => access_token}
    params.merge!(options)
    url = URI.parse("https://graph.facebook.com/me/photos")

    req = Net::HTTP::Post::Multipart.new
"#{url.path}?#{params.to_query}",
    "file" => UploadIO.new(photo, mime_for_file(photo), photo.path)

    n = Net::HTTP.new(url.host, url.port)
    n.use_ssl = true
    n.verify_mode = OpenSSL::SSL::VERIFY_NONE
    n.start do |http|
      http.request(req)
    end
  end

private
  def mime_for_file(f)
    m = MIME::Types.type_for(f.path.split('').last)
    m.empty? ? "application/octet-stream" : m.to_s
  end
end